Internet telephony encompasses a number of technologies for the transport of voice traffic over Internet Protocol (IP) networks. IP telephony can be divided into a media plane, a signaling plane, and call control plate. The media plane provides functionality required for media transport, such as packetization of voice data, packet delivery, and media playout at the destination. The signaling and call control plane provides functionality required to set up, tear down, and manage calls.
One aspect of Internet Telephony is the interworking of the IP network with the existing Public Switched Telephone Network (PSNT). In the context of PSTN interworking, the media and signaling planes include expanded functionality in order to connect the different network types. Thus, the media plane incorporates components which translate and map the voice data between a circuit switched network and an IP (packet) network, enabling it to act as a gateway between the two different means of media transport. Similarly, the signaling and call control plane incorporates components which translate and map signaling and call control protocols between PSTN and IP networks, in order to set up, tear down, and manage calls which traverse both types of network.
The development of common protocols and architectures for the PSTN interworking function is a major focus of several standards bodies, including the Internet Engineering Task Force (IETF) and International Telecommunication Union (ITU). While this is a large task requiring the resolution of many technical issues, one general architecture that has emerged in which the media plane and signaling and call control plane are viewed as distinct elements. The media component is referred to as a Media Gateway (MG). The signaling and call control component is further divided into two elements. A Media Gateway Controller (MGC) both controls the MG remotely, and handles IP-side signaling and call control with peer elements on the IP network. In addition, a Signaling Gateway provides the mapping and translation between the PSTN and IP signaling and call control protocols. One problem is that the general architecture does not necessarily specify the implementation of such components. For example, the Signaling Gateway and the MGC could be implemented as a single, integrated component.
The MGC and MG are configured in a master (MGC)—slave (MG) relationship, and multiple MGs may be under the control of a single MGC. Regardless of the number of MGs under a given MGC, or the actual physical implementation of the MG, the MGC views each MG under its control as a distinct entity with which it communicates via a well-specified software interface. The various protocols that are being developed define standard sets of media processing capabilities, as well as the MGC-MG interface. Current protocols under development within the IETF include the Media Gateway Control (MEGACO) and Media Gateway Control Protocol (MGCP). Within the ITU, H.248 is the standard for the interface.
Because the MGC's only view of the MG is via the standard interface, it has no visibility into how the actual media resources are configured behind the interface in order to support the capabilities required by the interface. The media resources may be part of an integrated hardware platform (e.g., DSPs, controlling processors, and buses), or alternatively, a collection of distinct platforms, coordinated and managed by software which presents the standard MG interface to the MGC.
Thus, it is desirable to provide a virtual Media Gateway (MG) composed of multiple standalone media gateways. It would also be desirable to allow an outside entity, for example, a Media Gateway Controller (MGC), to transmit messages to a virtual Media Gateway and receive messages from a virtual Media Gateway and allow the outside entity to view the virtual Media Gateway as a single Media Gateway.